Process and method for continuous, non lot-based integrated circuit manufacturing

ABSTRACT

A method for continuous, non lot-based manufacturing of integrated circuit (IC) devices of the type to each have a unique fuse identification (ID) includes: reading the fuse ID of each of the IC devices; advancing multiple lots of the IC devices through, for example, a test step in the manufacturing process in a substantially continuous manner; generating data, such as test data, related to the advancement of each of the IC devices through the step in the process; and associating the data generated for each of the IC devices with the fuse ID of its associated IC device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No.10/205,918,filed Jul. 25, 2002, which is a continuation of application Ser. No.09/137,781, filed Aug. 20, 1998, now U.S. Pat. No. 6,427,092, issuedJul. 30, 2002, which is a continuation of application Ser. No.08/822,731, filed Mar. 24, 1997, now U.S. Pat. No. 5,856,923, issuedJan. 5, 1999, which is related to the following applications: Ser. No.08/591,238, filed Jan. 17, 1996, now abandoned; Ser. No. 08/664,109,filed Jun. 13, 1996, now U.S. Pat. No. 5,895,962, issued Apr. 20, 1999;Ser. No. 08/785,353, filed Jan. 17, 1997, now U.S. Pat. No. 5,927,512,issued Jul. 27, 1999; Ser. No. 08/801,565, filed Feb. 17, 1997, now U.S.Pat. No. 5,844,803 issued Dec. 1, 1998; Ser. No. 08/806,442, filed Feb.26, 1997, now U.S. Pat. No. 5,915,231, issued Jun. 22, 1999; and Ser.No. 08/871,015, filed Jun. 6, 1997, now U.S. Pat. No. 5,907,492, issuedMay 25, 1999. The disclosure of each of the previously referenced U.S.patent applications and patents is hereby incorporated by reference inits entirety.

BACKGROUND OF THE INVENTION

Field of the Invention: The present invention relates in general tointegrated circuit (IC) manufacturing and, more specifically, to methodsfor tracking IC devices in a substantially continuous flow of IC devicesfrom multiple lots through one or more steps in an IC manufacturingprocess.

State of the Art: Integrated circuits (ICs) are small electroniccircuits formed on the surface of a wafer of semiconductor material,such as silicon, in an IC manufacturing process referred to as“fabrication.” Once fabricated, ICs are probed to evaluate a variety oftheir electronic characteristics, cut from the wafer on which they wereformed into discrete IC dice or “chips,” and then assembled for customeruse using various well-known IC packaging techniques, including leadframe packaging, Chip-On-Board (COB) packaging, and flip-chip packaging.

During the manufacturing process, ICs generally undergo a variety oftests to ensure they will function properly once shipped. Testingtypically involves a variety of known test steps, such as speed grading,burn-in, and final, which test ICs for defects and functionality andgrade ICs for speed.

ICs are typically tracked through the fabrication, probe, assembly, andtest steps described above so correlations can be found between theresults of tests performed on ICs in the test steps and the“path” theICs took through the manufacturing process. For example, by tracking agroup of ICs through the manufacturing process, it might be determinedthat ICs wire-bonded on a particular wire-bonding machine have anunusually high failure rate when tested. Similarly, it might bedetermined that a test machine itself is failing a disproportionatenumber of ICs. In either case, tracking ICs through the manufacturingprocess allows the source of a problem to be pinpointed and addressed.

As shown in FIG. 1, a conventional procedure 10 for tracking ICs througha process step 12 in an IC manufacturing process involves the use of lotnumbers for the ICs. Lot numbers are first assigned to wafers duringfabrication. Typically, a group of 20-50 wafers receives a single uniquelot number (e.g., 36/1/9970). As the group of wafers proceeds to probe,the wafers are typically split into several sub-lots, with each sub-lotbeing assigned a new lot number (sometimes referred to as a “sub-lot”number) that is a modified form of the group's original lot number(e.g., 36/1/9970/0, 36/1/9970/1, . . . ). As the group continues throughthe manufacturing process, sub-lots are split and re-split for a varietyof reasons until the group is typically split into many sub-lots, allhaving a unique lot number that is a modified form of the group'soriginal lot number.

In the conventional tracking procedure 10, a sub-lot (e.g., sub-lot H)is received from an input queue 14 where sub-lots wait to proceedthrough the process step 12. The process step 12 may be any step in theIC manufacturing process including, for example, probe, wafer saw, speedgrading, burn-in, or final testing.

As a sub-lot advances through the process step 12, data 16 related tothe process step 12 is generated. Such data 16 may include, for example:an identification of the processing equipment and the operatingpersonnel for the process step 12; information regarding the set-up ofthe process step 12; the time and date the sub-lot advanced through theprocess step 12; and yield and test results from the process step 12.

Once a sub-lot has advanced through the process step 12, a processreport 18 is manually or automatically generated based on the generateddata 16. To associate the report 18, and hence the data 16, with the ICsin the sub-lot, and thus track the ICs through the process step 12, thereport 18 lists the lot number (e.g., “H”) of the ICs in the sub-lot.Typically, the report 18 also physically accompanies the sub-lot throughthe remainder of the manufacturing process to insure that the data 16 iscorrelated with the ICs in the sub-lot, although this is not necessaryif other indicia identifying the lot number of the ICs in the sub-lotphysically accompany the sub-lot through the manufacturing process.

With the report 18 generated, a processed sub-lot (e.g., sub-lot H) iscleared from equipment associated with the process step 12 to an outputqueue 20 to prepare the process step 12 for processing another sub-lot(e.g., sub-lot I). Once the processed sub-lot is cleared, the nextsub-lot can be processed. This “clearing” process is necessary becauseif two sub-lots (e.g., sub-lots H and I) proceed through the processstep 12 in a continuous manner, the conventional tracking procedure 10is unable to correlate the data 16 and the process report 18 generatedas each of the two sub-lots proceed with the correct sub-lot. Instead,the data 16 for the two sub-lots is mixed, causing the conventionaltracking procedure 10 to fail to uniquely track the two sub-lots throughthe process step 12.

The conventional tracking procedure described above is problematicbecause it makes inefficient use of often very expensive manufacturingand test equipment and other resources by leaving sub-lots “parked” ininput queues while process reports are generated and the equipment iscleared of already processed sub-lots. In process steps which usemultiple machines in parallel to process a sub-lot, some machines may beidle while other machines finish their allotment from the sub-lot beingprocessed and the next sub-lot waits in an input queue. In addition,generation of the process reports, as well as clearing a processedsub-lot from equipment, often requires laborious manual work byoperating personnel. Further, a process report that must physicallyaccompany a sub-lot through the manufacturing process may become lost ordamaged. And thus is not as reliable a means of tracking ICs as isdesired.

As described in U.S. Pat. Nos. 5,301,143, 5,294,812, and 5,103,166, somemethods have been devised to aid quality control personnel in trackingICs undergoing failure analysis back to the wafer from which they come.By tracking the ICs back to their wafer, test data related to the ICscan be correlated to the wafer to pinpoint possible problems with thewafer. Such methods take place “off” the manufacturing line, and involvethe use of electrically retrievable identification (ID) codes, such asso-called “fuse IDs,” programmed into individual ICs to identify theICs. Fuse IDs and other electrically retrievable ID codes are typicallyprogrammed into ICs by blowing selected fuses or anti-fuses in circuitryon the ICs so that the circuitry outputs the ID code when accessed.Unfortunately, none of these methods addresses the inefficiency problemscaused by the conventional lot-based tracking procedure described above.

Therefore, there is a need in the art for a procedure for tracking ICsthrough an IC manufacturing process that uses manufacturing resourcesmore efficiently. Such a procedure should not leave equipment idle whileICs wait to be processed. In addition, such a procedure should achieve alevel of reliability not reached by conventional tracking procedures.

BRIEF SUMMARY OF THE INVENTION

An inventive method for tracking integrated circuit (IC) devices of thetype to each have a substantially unique identification (ID) code (e.g.,a fuse ID) through a step in an IC manufacturing process includes:reading the ID code of each of the IC devices; advancing multiple lotsof the IC devices through the step in the manufacturing process in asubstantially continuous manner; generating data, such as processingequipment data or test data, related to the advancement of each of theIC devices trough the step in the process; and associating the datagenerated for each of the IC devices with the ID code of its associatedIC device.

-   -   By associating the data with the ID codes, the inventive method        allows the IC devices to be tracked through the step in the        process. Further, because multiple lots of the IC devices can        advance through the step in the manufacturing process        continuously, manufacturing resources are used more efficiently.        In addition, because the ID codes and associated data read and        generated using the inventive method need not physically        accompany ICs as they progress through the manufacturing        process, the inventive method is more reliable than conventional        tracking procedures.

In another embodiment, a method of manufacturing IC devices fromsemiconductor wafers includes: providing wafers in multiple lots;fabricating ICs on the wafers; causing each of the ICs to permanentlystore a substantially unique ID code, such as a fuse ID; separating theICs from their wafers to form IC dice; assembling the IC dice into ICdevices; reading the IC code from the IC in each of the IC devices;testing each of the IC devices; while testing the IC devices: advancingthe IC devices from the multiple lots of wafers through at least onetest step in a substantially continuous manner; generating data relatedto the advancement of each of the IC devices through the test step; andassociating the data generated for each of the IC devices with the IDcode of the IC in its associated IC device.

In a further embodiment, a method for correlating variables related toan IC manufacturing process with variables related to the performance ofIC devices as they advance through the process includes: causing each ofmultiple ICs from multiple lots to permanently store a substantiallyunique ID code, such as a fuse ID; reading the ID code from each of theIC devices; advancing the IC devices from the multiple lots through atleast one step in the manufacturing process in a substantiallycontinuous manner; while the IC devices advance through the step in themanufacturing process, generating data related to process variablesassociated with the step in the process; generating data related tovariables associated with the performance of at least some of the ICdevices as they advance through at least one step in the manufacturingprocess; and associating the process variable-related data and theperformance variable-related data generated for each of the IC deviceswith the ID code of the IC device associated with the data to correlatethe process variables with the performance variables.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram showing a process step in a conventionallot-based integrated circuit (IC) manufacturing process; and

FIG. 2 is a flow diagram showing a process step in a substantiallycontinuous, non lot-based IC manufacturing process in accordance withthe present invention.

DETAILED DESCRIPTION OF TIE INVENTION

As shown in FIG. 2, an inventive method 30 for tracking integratedcircuit (IC) devices through a step 32 in an IC manufacturing processincludes a step 34 of receiving IC devices from multiple, mixed lots 36.It will be understood by those having skill in the field of thisinvention that the invention is applicable to any IC devices, includingDynamic Random Access Memories (DRAMs), Static Random Access Memories(SRAMs), Synchronous DRAMs (SDRAMs), processors, Application SpecificICs (ASICs), Read Only Memory (ROM) ICs, Electrically ErasableProgrammable ROM (EEPROM) ICs, and to mixtures of different types of ICdevices. Further, it will be understood that the step 32 may be any stepin an IC manufacturing process, including assembly and test steps. Itwill also be understood that the step 32 may encompass processing by asingle machine, part of a machine, many machines operating in series orparallel, or any combination thereof. In addition, it will be understoodthat the step 34 of receiving IC devices from multiple, mixed lots 36 iswithout regard to the lots from which the IC devices come, and thusallows a more efficient use of processing equipment than traditionallot-based procedures. It will also be understood, of course, thatalthough the present invention is described as being implemented in asingle process step 32 for ease of understanding, the invention moretypically is implemented on a series of process steps, such as allback-end test steps.

The IC devices are each programmed with a unique identification (ID)code, such as the well-known fuse ID described above. Briefly, a fuse IDis programmed in an IC device by selectively blowing fuses or anti-fusesin a circuit on the IC device so that when the circuit is accessed, itoutputs an ID code. Although it is preferable that the ID codeprogrammed into each IC device be unique by specifying, for example, alot number, wafer number, and wafer position for the IC device, it isnot necessary to implement the present invention. For example, if the IDcode is the same for all IC devices derived from the same semiconductorwafer, or from the same lot, it will work for purposes of the presentinvention.

Before or after the IC devices progress through the process step 32,their ID codes are read and stored in a computer as data 38. As the ICdevices progress through the process step 32, data 40 related to theprocess step 32 is generated for each IC device. Such data 40 mayinclude, for example, process variables such as the processing equipmentused, the operating personnel present, the set-up, and the time and dateof processing for the process step 32, and performance variables such asyield and test results from the process step 32. The set-up for theprocess step 32 may include, for example, a standard set-up or a set-upin accordance with a Special Work Request (SWR) by engineeringpersonnel.

The ID code data 38 and process-related data 40 may be automaticallycorrelated by computer with data from process steps prior to the processstep 32 through reference to the ID codes common to the ID code data 38generated in the process step 32 and ID code data generated in the priorprocess steps. As a result, correlations can be found between processvariables, such as the processing equipment used, and performancevariables, such as test results. Thus for example, it might be discernedthat the IC devices derived from a particular section of thesemiconductor wafers provided by a particular supplier have an unusuallyhigh failure rate at a particular test step. The process of correlationis preferably performed in real time so information is availableimmediately, although it is within the scope of the present invention toperform the correlation at a later time.

Once the IC devices have advanced through the process step 32, theprocessed IC devices are output from the process step 32 to mixed outputlots 42. It should be understood that, in some cases, the processed ICdevices must be cleared from processing equipment before other ICdevices can be processed, and in other cases, such as in serial-feedmachines, processed IC devices are being output from the process step 32while other IC devices are advancing through the process step 32 andstill other IC devices are being received by the process step 32. Any ofthese cases fall within the scope of the present invention.

It should be understood that by reading the ID codes of processed ICdevices and associating those codes with data generated duringprocessing, the inventive method 30 avoids the need for lot-basedmanufacturing altogether. The input and output lots 36 and 42 may thenbe mixed without regard to lots, and the processing of IC devicesthrough the process step 32 may proceed in a substantially continuousfashion, thus dramatically improving the utilization of processingequipment. In additions because the ID codes and associated data readand generated using the inventive method need not physically accompanyICs as they progress through the manufacturing process, the inventivemethod is more reliable than conventional tracking procedures.

Although the present invention has been described with reference to aparticular embodiment, the invention is not limited to this describedembodiment. For example, the present invention includes within its scopethe manufacture of Single In-line Memory Modules (SIMMs) and DualIn-line Memory Modules (DIMMs), as well as the IC devices describedabove. Thus, the invention is limited only by the appended claims, whichinclude within their scope all ods that operate according to theprinciples of the invention as described.

1. A method for tracking a device in a process comprising: forming aunique identification code using a fuse in the device for reading theunique identification code of the device; advancing the device throughthe manufacturing process; generating data related to the advancement ofthe device through a portion of the manufacturing process; andassociating the data generated for the device with the uniqueidentification code.
 2. The method of claim 1, wherein each integratedcircuit device of the plurality of integrated circuit devices isprogrammed with at least one substantially unique, electricallyretrievable identification code for the reading of the at least oneidentification code of each integrated circuit device of the pluralityof integrated circuit devices comprising electrically retrieving the atleast one substantially unique, electrically retrievable identificationcode of each integrated circuit device of the plurality of integratedcircuit devices.
 3. The method of claim 1, wherein each integratedcircuit device of the plurality of integrated circuit devices isprogrammed with at least one unique fuse identification code for thereading of the at least one identification code of each integratedcircuit device of the plurality of integrated circuit devices comprisingreading the at least one unique fuse identification code programmed intoeach integrated circuit device of the plurality of integrated circuitdevices.
 4. The method of claim 1, wherein advancing the plurality ofintegrated circuit devices through the manufacturing process includesadvancing the plurality of integrated circuit devices through anassembly step.
 5. The method of claim 1 wherein advancing the pluralityof integrated circuit devices through the manufacturing process includesadvancing the plurality of integrated circuit devices through a testprocedure.
 6. The method of claim 1, further comprising reading the atleast one identification code of each integrated circuit device of theplurality of integrated circuit devices occurs before advancing theplurality of integrated circuit devices through the manufacturingprocess.
 7. The method of claim 1, wherein advancing the plurality ofintegrated circuit devices through the manufacturing process includesserially advancing each integrated circuit device of the plurality ofintegrated circuit devices through multiple machines associated with themanufacturing process.
 8. The method of claim 1 wherein advancing theplurality of integrated circuit devices through the manufacturingprocess includes advancing the plurality of integrated circuit devicesthrough parallel machines associated with the manufacturing process. 9.The method of claim 1, wherein generating data related to theadvancement of each integrated circuit device of the plurality ofintegrated circuit devices through the at least a portion of themanufacturing process comprises generating data selected from a groupconsisting of processing equipment data, processing personnel data,processing set-up data, time and date data, yield data, and test data.10. The method of claim 1, further comprising storing the at least oneidentification code of each integrated circuit device of the pluralityof integrated circuit devices, the associating of data generated foreach integrated circuit device of the plurality of integrated circuitdevices with the at least one identification code of its associatedintegrated circuit device comprising storing the data generated for eachintegrated circuit device of the plurality of integrated circuit devicesin association with the stored at least one identification code of itsassociated integrated circuit device.
 11. The method of claim 1, whereineach integrated circuit device of the plurality of integrated circuitdevices has an associated lot identification code and the associatingdata generated for each integrated circuit device of the plurality ofintegrated circuit devices with the at least one identification code ofits associated integrated circuit device comprising storing the datagenerated for each integrated circuit device of the plurality ofintegrated circuit devices in association with the lot identificationcode of its associated integrated circuit device.
 12. A method fortracking a process using a device in the process comprising: forming aunique identification code using a fuse in the device for reading theunique identification code of the device; advancing the device through afirst portion of the manufacturing process; forming a uniqueidentification code using a fuse in the device for reading the uniqueidentification code of the device associated with the first portion ofthe manufacturing process; advancing the device through a second portionof the manufacturing process; forming a unique identification code usinga fuse in the device for reading the unique identification code of thedevice associated with the second portion of the manufacturing process;generating data related to the advancement of the device through thefirst portion and the second portion of the manufacturing process; andassociating the data generated for the device with the uniqueidentification code for the first portion and the second portion of themanufacturing process.
 13. The method of claim 12, wherein eachintegrated circuit device of the plurality of integrated circuit devicesis programmed with at least one substantially unique, electricallyretrievable identification code for the reading of the at least oneidentification code of each integrated circuit device of the pluralityof integrated circuit devices comprising electrically retrieving the atleast one substantially unique, electrically retrievable identificationcode of each integrated circuit device of the plurality of integratedcircuit devices for advancing the plurality of integrated circuitdevices through an assembly step.
 14. The method of claim 12, whereineach integrated circuit device of the plurality of integrated circuitdevices is programmed with at least one unique fuse identification code,the reading of the at least one identification code of each integratedcircuit device of the plurality of integrated circuit devices comprisingreading the at least one unique fuse identification code programmed intoeach integrated circuit device of the plurality of integrated circuitdevices for advancing the plurality of integrated circuit devicesthrough a test procedure.
 15. The method of claim 12, wherein advancingthe plurality of integrated circuit devices through the manufacturingprocess includes advancing the plurality of integrated circuit devicesthrough one of an assembly step and a test procedure.
 16. The method ofclaim 12, further comprising reading the at least one identificationcode of each integrated circuit device of the plurality of integratedcircuit devices occurs before advancing the plurality of integratedcircuit devices through the manufacturing process wherein advancing theplurality of integrated circuit devices through the manufacturingprocess includes serially advancing each integrated circuit device ofthe plurality of integrated circuit devices through multiple machinesassociated with the manufacturing process.
 17. The method of claim 12,wherein advancing the plurality of integrated circuit devices throughthe manufacturing process includes advancing the plurality of integratedcircuit devices through parallel machines associated with themanufacturing process.
 18. The method of claim 12, further comprisingstoring the at least one identification code of each integrated circuitdevice of the plurality of integrated circuit devices for theassociating the data generated for each integrated circuit device of theplurality of integrated circuit devices with the at least oneidentification code of its associated integrated circuit devicecomprising storing the data generated for each integrated circuit deviceof the plurality of integrated circuit devices in association with thestored at least one identification code of its associated integratedcircuit device.
 19. The method of claim 12, wherein each integratedcircuit device of the plurality of integrated circuit devices has anassociated lot identification code and the associating data generatedfor each integrated circuit device of the plurality of integratedcircuit devices with the at least one identification code of itsassociated integrated circuit device comprising storing the datagenerated for each integrated circuit device of the plurality ofintegrated circuit devices in association with the lot identificationcode of its associated integrated circuit device.
 20. A tracking methodfor at least one integrated circuit device comprising: providing eachintegrated circuit device of a plurality of integrated circuit deviceswith at least one identification code; reading the at least oneidentification code of each integrated circuit device of the pluralityof integrated circuit devices; advancing the plurality of integratedcircuit devices through the manufacturing process in a substantiallycontinuous manner; generating data related to the advancement of eachintegrated circuit device of the plurality of integrated circuit devicesthrough at least a portion of the manufacturing process; and associatingthe data generated for each integrated circuit device of the pluralityof integrated circuit devices with the at least one identification codefor an associated integrated circuit device of the plurality ofintegrated circuit devices.